Various phosphorus compounds have been used as flame retardants with polymers such as polyurethanes. However, phosphorus compounds such as inorganic metal salts have been found difficult to apply or to retain in the polymer because of water solubility. Many of the organic phosphorus compounds are also volatile so that volatilization and exuding or bleeding of the compounds from the polymer occurs.
Another problem has been the formation of smoke since some phosphorus-organic compounds may reduce flammability, but cause considerable smoke evolution.
All organic based materials will burn, given proper conditions or proportions of heat and air. In recent years, plastic materials have found increasing use and many such materials pose a potential of fire wherever they are used.
Since polymers are organic materials, it would be impossible to make them non-combustible in all situations. Many additives and modifiers have been used to decrease the rate of burning and the spread of flame; however, most of the additives and modifiers so used are organic materials themselves which will burn under proper conditions. Many inorganic materials have also been used as flame retardants, but they are effective only when used in large amounts which are detrimental to polymer properties. Accordingly, known flame retardant additives, whether organic or inorganic, can be used in only small amounts or the physical properties of the polymer will be adversely affected.
The main cause of fire as a cause of death has been overlooked in the quest for better flame retardants. The problem of deaths caused by smoke inhalation remains.
It is not surprising that smoke reduction technology has not kept pace with flame reduction technology since it has seemed apparent to those skilled in the art that a system for reducing both smoke and flame would not be feasible. It was heretofore believed that smoke propagation was due to incomplete oxidation of the volatile products of pyrolysis and that smoke reduction could be achieved only by more complete oxidation, which inherently meant more flame. Conversely, increased smoke propagation was believed to be the natural and immutable consequence of flame reduction (i.e., reduced combustion).
Accordingly, there is a great need for polymer materials having reduced smoking characteristics, which are flame retardant, and which contain smoke and flame controlling additives in amounts insufficient to adversely affect the physical properties of the polymer.